The application of fluent process chemicals, such as photoresist used in semiconductor substrate photolithography, typically requires at least two chamber conditions. Under the first chamber condition, fluent process chemical is deposited onto the substrate. This is preferably executed with a minimum distance separating a dispense tip, typically extending over the substrate within the process chamber, and the target substrate. If a significant distance exists between the tip and the substrate, the applied process chemical may splash, resulting in an uneven application.
A second chamber condition is required for the even distribution of applied chemical across the substrate, such as for a planarization stage in a photolithography coat process. Traditionally, the substrate is spun at high speeds and high exhaust flows to accomplish this. However, it is advantageous to provide a concentrated solvent vapor environment to promote this even distribution. In the past, such concentrated vapor environments have posed risks to personnel in the vicinity of the process chamber since an exhaust flow necessary to avoid pollution of an operator workspace typically decreases solvent concentration while creating vortices above the spinning substrate. Such vortices typically result in the deposition of contaminants on the substrate. Further, it has been difficult to provide an environment consistently saturated with solvent, particularly for the first substrates processed after a period of disuse, leading to a lack of uniformity in solvent concentration referred to as "green cup".
A develop subprocess further benefits from high exhaust flow to minimize atomized develop spray particles from escaping into the local process environment. However, as previously indicated, such a high exhaust flow in known systems results in undesirable vortices and flow patterns.